U.S. EPA’s Models for Establishing Cleanup Levels in Soil, Water, Buildings and Streets at Superfund Sites Stuart Walker U.S. Environmental Protection Agency Office of Superfund Remediation and Technology Innovation (OSRTI) Science and Policy Branch Presented to the IAEA EMRAS II Workgroup "NORM & Legacy Sites" in Vienna, Austria on September 23, 2009 Page-1 EPA
Purpose 1. Provide brief overview of EPA Superfund approach for selecting cleanup levels and use of risk/dose assessment 2. Provide overview on new and upcoming CERCLA risk assessment calculators, guidance, and training for Radionuclides Page-2 EPA
Part 1 EPA Superfund Approach for Selecting Cleanup Levels Page-3 EPA
EPA Addresses Site Cleanup Under Several Law s, Programs � Comprehensive Environmental Response, Compensation & Liability Act, CERCLA or “Superfund” � National Contingency Plan (NCP) is regulation for CERCLA � National Priorities List (NPL) guides EPA on which sites need further attention Page-4 EPA
What does a Superfund Site look like? � There are many different types of Superfund sites. »See following 4 pages for examples of radioactively contaminated sites. Page-5 EPA
Page-6 Nuclear Metals Inc. - Massachusetts EPA
Abandoned Uranium Mines Project – Navajo Nation Page-7 EPA
Welsbach/General Gas Mantle – New Jersey Page-8 EPA
Hanford – D Reactor / DR Reactor Remediation DR Reactor Interim Safe Storage Project D Reactor Surveillance and Maintenance Effluent Piping Removal Contaminated Soil Remediation Page-9 EPA
CERCLA Decision-making � CERCLA cleanup decisions are made site- specifically » Must comply with CERCLA and NCP � EPA Regional site managers » Removals – On Scene Coordinators (OSCs) » Remedial (and NTC-removals) – Remedial Project Managers (RPMs) Page-10 EPA
Nine CERCLA Remedy Selection Criteria � Two threshold criteria (both must be met) 1. Protect human health and the environment 2. Comply (attain or waive) with other federal and state laws: Applicable or Relevant and Appropriate Requirements (ARARs) — Protect current or future sources of drinking water (e.g., attain MCLs or more stringent state standards) Page-11 EPA
Nine CERCLA Remedy Selection Criteria (continued) � 6 CERCLA ARAR waivers 1. Interim Measure 2. Greater Risk to Health and the Environment 3. Technical Impracticability 4. Equivalent Standard of Performance 5. Inconsistent Application of State Requirements 6. Fund Balancing Page-12 EPA
Nine CERCLA Remedy Selection Criteria (continued) � Five balancing criteria (used to evaluate between potential remedies that meet threshold criteria) 1. Long-term effectiveness and permanence 2. Reduction of waste toxicity, mobility, or volume 3. Short-term effectiveness 4. Implementability 5. Cost Page-13 EPA
Nine CERCLA Remedy Selection Criteria (continued) � Two modifying criteria (information from public comment period that may modify remedial action) 1. State acceptance 2. Community acceptance Page-14 EPA
CERCLA Cleanup Levels � ARARs often determine cleanup levels � Where ARARs are not available or protective, EPA sets site-specific cleanup levels that » For carcinogens, represent an increased cancer risk of 1 x 10 -6 to 1 x 10 -4 —10 -6 used as “point of departure” —PRGs are established at 1 x 10 -6 » For non-carcinogens, will not result in adverse effects to human health (hazard index (HI) <1) � Address ecological concerns � To-be-considered (TBC) material may help determine cleanup level Page-15 EPA
CERCLA Cleanup Levels Are NOT NOT Based On � NRC decommissioning requirements (e.g., 25, 100 mrem/yr dose limits) 10 CFR 20 Subpart E » If used as an ARAR, 10 -6 still used as point of departure, and 10 -4 to 10 -6 risk range must be met � Guidance outside risk range and/or if expressed as a dose (# mrem/year). This includes: » DOE orders, NRC guidance (e.g., NUREGs), ICRP guidance, IAEA guidance, NCRP guidance, ANSI/HPS guidance, EPA/DHS PAGs, and Federal guidance Page-16 EPA
Risk-based Cleanup Levels for Radioactive Contamination � Radiation cleanup levels expressed as risk levels, not mrem [mSv] � Superfund uses “slope factors” in Health Effects Assessment Summary Tables (HEAST) instead of dose conversation tables to estimate cancer risk from radioactive contaminants » HEAST has been updated with new information from Federal Guidance 13 —Based on information in ICRP 72 Page-17 EPA
EPA/ITRC CERCLA Policy and Guidance Training � Four modules provide: 1. Radiation Regulatory Background and Case Studies 2. Overview of CERCLA Requirements 3. EPA CERCLA Radiation Guidance and Tools 4. Challenges of Long-Term Management of Radiation Sites Page-18 EPA
EPA/ITRC CERCLA Policy and Guidance Training, cont. � Five Live Internet rad CERCLA Policy Training sessions have been conducted » 838 total participants, including 163 EPA employees � An archived version of a live training session is available at: » http://www.clu-in.org/conf/itrc/radscleanup_060507/ � Archived version was accessed by users 3,282 times between January 1, 2008 and August 26, 2009. Page-19 EPA
Radiation Human Health Assessment Approaches � RISK APPROACH » Where risk is calculated directly by assigning a unit of risk for every unit of exposure (Cancer Slope Factor) and multiplying by the total exposure. � DOSE APPROACH » Where dose is calculated by multiplying a dose conversion factor by the total intake/exposure. » The calculated dose can also be multiplied by a probability coefficient to arrive at a risk value. Page-20 EPA
Radiation Human Health Assessment Approaches Risk = Exposure X Cancer Slope Factor Dose = Exposure X Dose Conversion Factor (DCF) Page-21 EPA
Inhalation Pathw ay Example: � RISK = (Inhalation Slope Factor) X (radionuclide concentration in air) X (breathing rate) X (exposure duration) � DOSE = (DCF) X (radionuclide concentration in air) X (breathing rate) X (exposure duration) Page-22 EPA
Basis for Risk and Dose Approaches RISK DOSE � Lifetime exposure to an � Annual exposure to an average individual with a reasonable member of the “critical group” maximum exposure (EPA) (NRC) � Risk is a unitless measurement � Dose equivalent is measured in of the likelihood of an adverse units of rem, mrem, or sievert affect � Standards expressed in terms of � Standards expressed in terms of risk (e.g., EPA’s 10 -4 -10 -6 CERCLA dose equivalent (e.g., NRC’s 25 risk range) mrem/year) � Slope factors based primarily on � DCFs based on populations from US population other nations Page-23 EPA
Basis for Risk and Dose Approaches, cont. RISK DOSE � Age- and sex-dependent risk � Age-dependent (separate DCFs, models in Slope Factors for infants, children, and adults) � Slope Factor does not consider � DCFs consider genetic risk genetic risk � Considers causes of death other � Does not consider other than radiation-induced cancer competing causes of death � Low-LET & high-LET estimates � Dose equivalent includes both considered separately for each low-LET and high-LET radiation target organ multiplied by appropriate Relative Biological Effectiveness (RBE) factors Page-24 EPA
Basis for Risk and Dose Approaches (cont.) RISK DOSE � RBE for most sites = 20; RBE for � RBE for alpha radiation = 20 for breast =10; for leukemia =1 all sites � Estimates of absorbed dose to � Effective dose considers dose 16 target organs/tissues estimates to 12+ target organs (+ average of 10 other organs) � Lung dose based on absorbed � Lung dose based on average dose to tracheobronchial and dose to tracheobronchial, pulmonary regions nasopharyngeal and pulmonary regions � Variable length to integration � Fixed length of 50 years for period (< 110 years) integration period Page-25 EPA
Radiation Human Health Assessment Approaches � Dose values may be converted into risk and vice versa using conversion factors � Dose and Risk are closely related » [Risk = (total dose) X (probability coefficient in risk/unit dose)] � Risks converted from dose may vary as much as 10 times from risks based on slope factors for some types of exposure Page-26 EPA
Part 2 New and Upcoming Superfund Radiation Risk Calculators and Training Page-27 EPA
Guidance: Risk Assessment Q& A � Radiation Risk Assessment at CERCLA Sites: Q&A (12/99) OSWER Directive 9200.4-31P � Provides overview of current EPA guidance for radiation risk assessment � Written for users familiar with Superfund but not radiation � Adds some new guidance » Dose assessment only for ARAR compliance » No dose-based TBCs (including No 15 mrem/yr [0.15 mSv/yr] for selecting cleanup levels) » Direct exposure rate may supplement sampling Page-28 EPA
Guidance: Rad SSG � Soil Screening Guidance for Radionuclides [rad SSG] documents (10/00) OSWER Directives 9355.4-16A and 9355.4-16 » User Guide » Technical Background Document � Guidance to screen out areas, pathways, and/or radionuclides early in the process � Consistent with 1996 chemical SSG » 1 x 10 -6 and MCLs (leaching from soil) » Residential land use » Survey procedures for site characterization » Evaluates 5 soil to groundwater models » Accounts for technical differences of radiation Page-29 EPA
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